The present invention relates to a color separation transparency of a partial image in one of the primary colors blue, green, yellow or red or in black or white color, and to processes for the preparation thereof.
Color separation transparencies of this type are used for the preparation of relief structures in the plane of a recording material, from which embossing matrices are taken. By means of these embossing matrices for example, relief images are embossed in polyvinyl chloride films, and these relief images on projection give a multi-colored image of the original for the color separations.
Grid-wise screened images are produced by the ZOD (Zero-Order-Diffraction) technique which is known from the journal LASER u. Elektro-Optik No. 3/1976, pages 16/17. Three nickel matrices are produced from the relief images which, for example, correspond to three main color grid patterns in three photo-lacquer layers, and these matrices are used to emboss colorless thermoplastic films of polyvinyl chloride. These films are mechanically superposed. On projecting the superposed embossed images, using conventional projectors, colored projection images are obtained from the colorless relief images. The grid-like structuring is accomplished with relief grids of rectangular cross-section, the grid period being about 1.5 .mu.m. One nickel matrix of different relief depth is made for each color separation in yellow, magenta and cyan, having relief depths of about 1.2 .mu.m, 1.5 .mu.m and 1.8 .mu.m respectively, and the separate embossed images are generated using these matrices. The embossed images are superposed to give a three-layer relief image, from which colored images can be projected.
A disadvantage which makes the acceptance of this technique more difficult is the expensive preparation process with three completely separate working steps for making the individual embossed relief grids corresponding to the color separation. A further serious disadvantage is the necessary composing of the three separate relief images in true register to give the duplicate image required for the colored projection.
To overcome this disadvantage, it is proposed in German Patent Application No. P 26 57 246.3 (corresponding to U.S. application Ser. No. 861,491, filed Dec. 16, 1977 to compose the relief image in one plane from several relief partial images which are adjacent but do not overlap and have different grid depths. A further development of this technique is described in German Patent Application No. P 27 34 581.9 (corresponding to U.S. application Ser. No. 928,700, filed July 27, 1978), according to which grid structures for at least four projection colors, for example yellow, red, blue-violet and green, are used. White color is represented by grid-free partial areas. It was proposed to obtain black partial images by means of statistically random relief structures of 1-2 .mu.m depth.
To produce relief images of this type in one plane, German Patent Application No. P 27 34 580.8 (corresponding to U.S. application Ser. No. 928,701, filed July 27, 1978) describes a method in which the photo-lacquer layer is grid-wise exposed for the projection color green through to the greatest grid depth, and the grid depths of the partial images are then reduced down to the depths necessary for the particular desired projection color red, yellow, blue or white by exposure through color separations. For the color white, the grid structure must be almost completely removed. The green partial image areas are not exposed again since, as mentioned above, the greatest grid depth for the projection color green has already been fully exposed.